Relationship between stroke frequency and hand propulsive force in the front crawl

Abstract

This study aims at clarifying the factors responsible for the change in hand propulsive force when the stroke frequency was changed. Eight male swimmers performed five 20m-front crawls. The first trial involved maximal effort, whereas the stroke frequency was controlled during the next four trials. The instructed stroke frequencies were 70%, 80%, 90%, and 100% of the stroke frequency at the maximal effort trial. To calculate the hand

How do swimmers control their front crawl swimming velocity? Current knowledge and gaps from hydrodynamic perspectives

“…Figure 4(e) shows that both F hand and its propelling directional component T hand increased from 70% to 90% SF, peaked at 100% SF, and then decreased from 110% to 120% SF. The increase in the mean T hand was indirectly supported by Schnitzler et al (2011) who showed the propulsive impulse during one stroke cycle was unchanged among five velocity conditions (ranging from 60% to 100% of maximum velocity) with a similar method as Koga et al (2020Koga et al ( , 2021. Given that the stroke duration becomes shorter when increasing SF (34.8 − 51.8 Hz in the study by Schnitzler et al), the mean T hand should also have been increased in their study.…”

“…However, in combination with 3D underwater motion analysis, the direction of the fluid force acting on the hand can also be obtained. Here we present the results of experiments (Koga et al, 2020(Koga et al, , 2021 that measured the kinematic parameters of swimming motion and fluid mechanical parameters acting on the hand for a range of SF. In the following sub-sections, the impact of changing SF on other variables is discussed.…”

“…Changes in kinematic parameters (SL, v, V hand and α) when increasing SF Figure 4(a), which was created by the authors using the experimental data presented in Koga et al (2020Koga et al ( , 2021), shows SL and � v at 70%, 80%, 90%, 100%, 110% and 120% of the SF in the pre-measured maximal front crawl condition. The figure shows that � vpeaked at SF = 100% and then plateaued or slightly decreased as the SF increased to 110% and 120%.…”

“…In this section, we discuss how pressure around the hand, F hand and T hand change as SF increases. Figure 4(d), which was again created using experimental data presented in Koga et al (2020Koga et al ( , 2021), shows changes in average pressure on the palm side and dorsal side (average value of three pressure sensors put on each side) of a hand at six selected SF. As the pressure describes the fluid force acting on a unit area (m 2 ), F hand can be estimated by multiplying the area of the hand by the difference in the pressure between the palmand dorsal-side of the hand (Takagi & Wilson, 1999).…”

“…These methods enable researchers to estimate D (and consequently T, when the swimmer maintains a constant velocity) acting on the whole body but do not provide information on the sources of the total forces. Therefore, pressure sensors have been used to estimate T hand in recent years (Koga et al, 2020(Koga et al, , 2021Kudo et al, 2012;Tsunokawa et al, 2019).…”